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// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
'use strict';
base.require('base.guid');
base.exportTo('base', function() {
/**
* KeyEventManager avoids leaks when listening for keys.
*
* A common but leaky pattern is:
* document.addEventListener('key*', function().bind(this))
* This leaks.
*
* Instead do this:
* KeyEventManager.instance.addListener('keyDown', func, this);
*
* This will not leak. BUT, note, if "this" is not attached to the document,
* it will NOT receive input events.
*
* Conceptually, KeyEventManager works by making the this refrence "weak",
* which is actually accomplished by putting a guid on the thisArg. When keys
* are received, we look for elements with that guid and dispatch the keys to
* them.
*/
function KeyEventManager(opt_document) {
this.document_ = opt_document || document;
if (KeyEventManager.instance)
throw new Error('KeyEventManager is a singleton.');
this.onEvent_ = this.onEvent_.bind(this);
this.document_.addEventListener('keydown', this.onEvent_);
this.document_.addEventListener('keypress', this.onEvent_);
this.document_.addEventListener('keyup', this.onEvent_);
this.listeners_ = [];
}
KeyEventManager.instance = undefined;
KeyEventManager.resetInstanceForUnitTesting = function() {
if (KeyEventManager.instance) {
KeyEventManager.instance.destroy();
KeyEventManager.instance = undefined;
}
KeyEventManager.instance = new KeyEventManager();
}
KeyEventManager.prototype = {
addListener: function(type, handler, thisArg) {
if (!thisArg.keyEventManagerGuid_) {
thisArg.keyEventManagerGuid_ = base.GUID.allocate();
thisArg.keyEventManagerRefCount_ = 0;
}
thisArg.classList.add('key-event-manager-target');
thisArg.keyEventManagerRefCount_++;
var guid = thisArg.keyEventManagerGuid_;
this.listeners_.push({
guid: guid,
type: type,
handler: handler
});
},
onEvent_: function(event) {
// This does standard DOM event propagation of the given event, but using
// guids to locate the thisArg for each listener. See event_target.js for
// notes on how this works.
var preventDefaultState = undefined;
var stopPropagationCalled = false;
var oldPreventDefault = event.preventDefault;
event.preventDefault = function() {
preventDefaultState = false;
oldPreventDefault.call(this);
};
var oldStopPropagation = event.stopPropagation;
event.stopPropagation = function() {
stopPropagationCalled = true;
oldStopPropagation.call(this);
};
event.stopImmediatePropagation = function() {
throw new Error('Not implemented');
};
var possibleThisArgs = this.document_.querySelectorAll(
'.key-event-manager-target');
var possibleThisArgsByGUID = {};
for (var i = 0; i < possibleThisArgs.length; i++) {
possibleThisArgsByGUID[possibleThisArgs[i].keyEventManagerGuid_] =
possibleThisArgs[i];
}
// We need to copy listeners_ and verify the thisArgs exists on each loop
// iteration because the event callbacks can change the DOM and listener
// list.
var listeners = this.listeners_.concat();
var type = event.type;
var prevented = 0;
for (var i = 0; i < listeners.length; i++) {
var listener = listeners[i];
if (listener.type !== type)
continue;
// thisArg went away.
var thisArg = possibleThisArgsByGUID[listener.guid];
if (!thisArg)
continue;
var handler = listener.handler;
if (handler.handleEvent)
prevented |= handler.handleEvent.call(handler, event) === false;
else
prevented |= handler.call(thisArg, event) === false;
if (stopPropagationCalled)
break;
}
// We want to return false if preventDefaulted, or one of the handlers
// return false. But otherwise, we want to return undefiend.
return !prevented && preventDefaultState;
},
removeListener: function(type, handler, thisArg) {
if (thisArg.keyEventManagerGuid_ === undefined)
throw new Error('Was not registered with KeyEventManager');
if (thisArg.keyEventManagerRefCount_ === 0)
throw new Error('No events were registered on the provided thisArg');
for (var i = 0; i < this.listeners_.length; i++) {
var listener = this.listeners_[i];
if (listener.type == type &&
listener.handler == handler &&
listener.guid == thisArg.keyEventManagerGuid_) {
thisArg.keyEventManagerRefCount_--;
if (thisArg.keyEventManagerRefCount_ === 0)
thisArg.classList.remove('key-event-manager-target');
this.listeners_.splice(i, 1);
return;
}
}
throw new Error('Listener not found');
},
destroy: function() {
this.listeners_.splice(0);
this.document_.removeEventListener('keydown', this.onEvent_);
this.document_.removeEventListener('keypress', this.onEvent_);
this.document_.removeEventListener('keyup', this.onEvent_);
},
dispatchFakeEvent: function(type, args) {
var e = new KeyboardEvent(type, args);
return KeyEventManager.instance.onEvent_.call(undefined, e);
}
};
KeyEventManager.instance = new KeyEventManager();
return {
KeyEventManager: KeyEventManager
};
});
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